This blog is devoted to the application of optical fibers in photography. I have several homemade (DIY) flash adapters channeling the light from the flash close to the lens. The technique can be used mainly for macro photography, but I will show examples for wide angle close focus techniques as well. The recent version is called fiberstrobe V3, hence the name of the blog is "fiberstrobe".

Sunday, January 5, 2014

Sony nex ring flash adapter step by step

Although I already have a
nice optical fiber based ring flash adapter (see project here) I thought that I
will try a simpler alternative solution. The idea popped up in my mind during
eating rice pudding. The plastic cup just looked like a perfect core for a ring
adapter.

For
attaching the adapter to the lens I used my usual solution with a foam layer.
So I trimmed back a bit the cup and glued into the foam. After that I cut out
the hole for the lens.

It’s
important to block the reflection light slipping back from the cup, therefore I
needed an isolation ring surrounding the lens.

The
most difficult part was to channel the light into the cup. I could have used
optical fibers but this time I wanted to use something else. Cardboard is an
option but I wanted something more flexible. Then I remembered that I have a
punctured inner tube from my bicycle I put away for some tinkering project (I
wanted to make such DIY speed straps). Although the diameter was to small gluing
the rubber seemed to be simple. I covered the inner part with aluminium foil
backed tape (the must to have product for all strobe modifier).

After
attaching the inner ring (inside covered with black non reflecting thin foam)
to the cup I also applied some aluminium tape to cover the resulting channel
around the lens.

I cut
a hole into the cup to attach the rubber tube to it. It was a bit tricky to
align the tube to the cup and glue it. The light is going through this hole. The
problem is that now the light is channelled only to the upper part of the ring
and the light distribution is not even. Actually this is the major problem of
this kind of ring flash adapter design. See below the light pattern at this
stage:

To
improve the light distribution I glued a V-shaped reflector to this part of the
inner ring to reflect the light sideways. It’s improved the outputbut it was still far from perfect, so I also
attached a blocking panel to this upper part (included some small holes to let
some light through).

Better
but not yet perfect, so I added a diffuser panel.

It
looks almost perfect, but I was cheating a bit by overexposing the photo.
Actually some strange thing happened at this stage I guess due to some light
reflected back from this diffusor panel, the camera TTL is tended to overexpose
the photos. In close macros this reflected light was not a big problem but in
case of distant subjects it was visible on the photos.

In addition,
the light was still stronger in the upper part of the scene. In landscape
format, it’s not a big deal and in real photos it has even a more natural effect
(sun is shining high from the sky). However,
in case of portrait format the uneven light distribution is visible (see photos above).

I tried to construct a more complexdiffusor panel blocking the light slippage,
and I also added some reflecting panel to the upper part:

You may tell that the
light in the final version is not that pretty but it’s actually quite even. It’s
for macro, therefore the catch light reflected in the eyes is not that
important.

So
this is the final version. It can be folded and put into a small box for
transport:

How
does it perform? Just perfect. The light output is enough to use the biggest F
numbers with your macro lens at base iso. The light distribution is even, just
what you would expect from a ring flash: